1. Technical Field
The invention relates to an electromagnetic contactor that utilizes an electromagnet device to open or close a contact point, and more specifically, to a mechanism for preventing the bounce of a movable contact support when a movable iron core is released.
2. Prior Art
An electromagnetic contactor generally has a structure in which a movable contact support connected to a movable iron core of an electromagnet device retains a movable contact for each phase. In such a contactor, a mold frame for guiding the movable contact support in a slidable manner is fixed with a pair of front and rear fixed contacts for respective phases. In this structure, when an electromagnetic coil is excited to attract a movable iron core, the movable contact bridges the fixed contact to close the cable run, and when the electromagnetic coil is demagnetized, the released movable iron core is driven by the spring force of a return spring and the movable contact is separated from the fixed contact to open the cable run. In this case, the released movable iron core collides with the mold frame, and stops. This poses a risk in which the bounce of the movable contact support causes the once-separated movable contact to abut with the fixed contact, thus closing the cable run again.
A known electromagnetic contactor for preventing this is disclosed in Japanese Laid Open Utility Model Publication No. 64-16043, and is configured such that the base bottom face of the movable contact support abutted with the back face of a movable iron core has a step (different height) so that the movable iron core is inclined by this difference in height when the movable iron core collides with the mold frame, thereby preventing the movable contact support to bounce.
FIG. 7 is a longitudinal sectional view of an electromagnetic contactor illustrating another conventional example that is similar to the above-described one shown in Japanese Laid Open Utility Model Publication No. 64-16043. Hereinafter, the electromagnetic contactor will be newly described based on this. In FIG. 7, an electromagnet device consists of: a fixed iron core 2 having an electromagnetic coil 1; and a movable iron core 4 that is attracted toward the fixed iron core 2 by activation of the coil against the elastic force of a return spring 3. The back face of the movable iron core 4 is connected with a movable contact support 6 via a plate spring 5 and the movable contact support 6 retains a movable contact 7 having each phase. The movable contact support 6 is slidably guided by a mold frame 8 in the left-and-right direction of FIG. 7. The mold frame 8 is fixed with a pair of front and rear fixed contacts 9 for each phase.
In the “released” condition of the contactor of FIG. 7, a base section 6a of the movable contact support 6 abutting the back face of the movable iron core 4 faces a mold frame 8, while one end thereof (shown at the lower end portion of FIG. 7) abuts with the mold frame 8. On the other hand, the other end of the base section 6a (shown at the upper end portion of FIG. 7) is spaced from the mold frame 8 by a step S provided at the lower end section (See FIGS. 8A and 8B). Each fixed contact 9 is integrally formed with a respective one of the two main terminals 10 and is attached with a terminal screw 11. The upper part of the mold frame 8 of FIG. 7 is also attached with a coil terminal 12 for supplying power to the electromagnetic coil 1 and is attached with a terminal screw 13.
FIGS. 8A and 8B show how the electromagnetic contactor of FIG. 7 operates, FIG. 8A showing the “linked” condition and FIG. 8B showing the “released” condition. When the electromagnetic coil 1 (FIG. 7) is excited in FIGS. 8A and 8B, the movable iron core 4 is attracted toward the fixed iron core 2, and the movable contact 7, retained by the movable contact support 6, moves left to bridge the space between the fixed contacts [[9,]] 9 as shown in FIG. 8A, resulting in the cable run between the main terminals 10 being closed. Thereafter, when the electromagnetic coil 1 is demagnetized to release the movable iron core 4, the spring force of the return spring 3 (FIG. 7) separates the movable iron core 4 from the fixed iron core 2 tb cause the movable contact 7 to be separated from the fixed contact 9, thereby opening the cable run.
Then, the movable iron core 4 driven by the return spring 3 collides with the mold frame 8 as shown in FIG. 8(B) via the lower end section of the base section 6a of the movable contact support 6 so that the stop position thereof is regulated. When the movable iron core 4 is stopped, a movable section consisting of the movable iron core 4 and the movable contact support 6 is rotated clockwise due to the presence of the space between the upper end section of the base section 6a and the mold frame 8, and due to this rotation, the kinetic energy of the movable sections 4 and 6 is consumed as a moment of rotational inertia to reduce the impact by the collision between the movable iron core 4 and the mold frame 8, thereby preventing reclosure of the cable run due to the bounce of the movable contact support 6.
The electromagnetic contactor is generally attached to a panel as shown in FIG. 7 such that the side to which the coil terminal 12 is provided (power source side) is at the top, and the body lies in a lateral direction. The electromagnetic contactor shown in Japanese Laid Open Utility Model Publication No. 64-16043 or in FIG. 7 is manufactured with such a step arrangement, provided at the top of the movable contact support.
In this case, the movable iron core 4 in the “released” condition in FIG. 7 supported by the mold frame 8 in a cantilever manner via the movable contact support 6 is inclined in a slightly anticlockwise direction due to the weight thereof, with the lower part of the movable iron core 4 abutted with the mold frame 8 via the movable contact support 6. Due to this, the movable iron core 4 in the “released” condition always collides with the mold frame 8 at the lower side to enable the upper side step to work effectively, and the movable iron core 4 rotates around the lower side to reduce the impact. This also applies to the electromagnetic contactor shown in Japanese Laid Open Utility Model Publication No. 64-16043. The movable contact support and the guide face of the mold frame have therebetween a gap by which the above-described inclination of the movable iron core is caused.
On the other hand, when a conventional electromagnetic contactor is attached such that the coil terminal 12 is provided at the lower side (i.e., the step of the movable contact support 6 is provided at the lower side), then the above-described inclination of the movable iron core 4 deprives the movable contact support 6 of the function of the step. As a result, the rotation of the movable iron core 4 in the “released” condition is not caused, and thus the effect for reducing the impact is not obtained. To prevent this, the conventional electromagnetic contactor has been fixed in one predetermined direction so that the coil terminal 12 is provided at the upper side.
However, the recent diversification of device layouts has created a need for an arrangement in which the electromagnetic contactor is attached such that the coil terminal 12 is provided at the lower side, but this style of attachment cannot provide the buffering effect at the release, as described above. In view of the above, it is an objective of the invention to provide such an electromagnetic contactor for reducing the impact by rotating the movable iron core at the release, by which the buffering effect can be obtained regardless of the whether the coil terminal is attached at the upper or lower side.